People were also warned to stay clear of coastal areas and not to go sightseeing.
The first wave generated by the earthquake was expected to hit the top of the North Island shortly before daylight today but police this morning said nothing appeared out of the ordinary.
The Coastguard Northern Region said the tsunami in Japan generated by the 8.9 magnitude earthquake created a marine threat to New Zealand.
That meant strong and unusual currents in the sea, rivers and estuaries.
There was a small potential for waves on beaches reaching a metre high between Ahipara and the Karikari Peninsula in the Far North and in the Bay of Islands.
The waves were expected to arrive over five hours and the Coastguard said the first may not be the largest.
"People in coastal areas are advised to stay off beaches, stay out of the water, sea, river and estuaries, including boating activities.
"Do not go sightseeing," said the Coastguard.
Overnight numerous boaties called the Coastguard for updates on the warnings
